Evaluation of some unconventional trees/plants as ruminant feeds
 in Central Vietnam

Introduction

In central Vietnam, the population of ruminants occupy around 45% of the total live stock in the whole country. Because of hard conditions (high temperature, low rainfall in the dry season), shortage of animal feed is a big problem for livestock development, particularly for grazing cattle. The main feed supplement for animals during the dry season is rice and maize straws and various crop residues. Quantity and quality of feed is usually limited, particularly the protein content. This is reflected in poor animal performance.

In recent years, there have been many studies on the of tree foliages as supplements for live stock (Leng 199). In central Vietnam, there are some indigenous trees that can be used as forages. Among these are:

"Trung Ca" (Muntingia calabura) belonging to the family Elaeocarpacae. It can grow everywhere (sandy land, humid areas, and high land area) and is well adapted to the dry season in central Vietnam. The farmers use it as shade tree around the homestead, and along the roads. Trung Ca is a tall tree with a large canopy of leaves but it has not been used for animals.

"Dam But"  (Hibiscus rosa-sinensis L.) belongs to the Malvacae family. It adapts and grows well during the dry season in Central Vietnam. The most common planting method is by stem cuttings. The tree is grown as a live fence. In some areas "Dam But" is fed to rabbits and goats.

Mulberry (Morus spp) belongs to the Moraceae Family (Subtype Angiosperms; Class Dicotyledons; Subclass Urticales) and there are several species. Mulberry leaves have been the traditional feed for silk worms. In Vietnam there are many varieties with high yield. It can produce 60 tonnes of fresh leaves/ha/year according to the National Sericulture Research Centre (2000). In recent years, the area of Mulberry has decreased due to reduced activities in silk processing and limited market.  The traditional way of using mulberry as animal feed in silk-producing areas is to feed ruminants with the residue left by the silk worm.

Trichanthera gigantea is a tree of the Acanthaceae family and is apparently native to the Andean foothills of Colombia (Rosales 1997). The tree was introduced into Vietnam in 1991 and has been readily adopted by farmers throughout the country because of its tolerance to a wide range of ecological conditions and apparent resistance to pest and diseases (Nguyen Ngoc Ha and Phan Thi Phan,1993; Nguyen Thi Hong Nhan et al 1996; Nguyen Thi Hong Nhan and Nguyen van Hon 1999; Nguyen Xuan Ba, personal observations).

The research described in this paper was aimed at the evaluation of the agronomic characteristics and the nutritive value of the above trees as ruminant feeds.

Materials and methods

The experiment was started in September, 2001 in the HUAF experimental farm in Hue City. The climate is tropical monsoon with a yearly rainfall around 3415cm, most of which occurs from August to January. The temperature range is 21 to 29 degrees C. Air humidity varies in the range 79 to 91%. The soil is sandy loam with the pH around 5.5 in the topsoil.

The above species of shrubs and trees were planted at the same time in September, 2001. Hibiscus rosa and Morus alba and Trichanthera gigantea were planted by stem cuttings. Muntingia calabura was planted by seedlings when their height was about 50 cm. The foliages were harvested when the plants reached 1 m height except for "Trung Ca" which was 2.5 m. The cutting point was  50 cm above ground level.

Samples of the foliages (leaves, petioles and young stems) were collected at harvest time and analysed according to the official methods of AOAC (1990). Cell wall components (NDF, ADF) were determined according to Van Soest et al (1991).  Rumen degradability were determined according to Ørskov et al (1980) using three fistulated crossbred cattle. In vitro  gas production method was measured following the method of Menke and Steingass (1988).

 Result and discussion

 Harvesting and foliage production

Trichanthera and Hibiscus had higher biomass yield than Mulberry and Muntingia (Table 1). It has been observed that all the above species grow faster in the spring season compared with the winter season in central Vietnam (Nguyen Xuan Ba, unpublished data). There appear to be good prospects for using Trichanthera,  Hibiscus and Mulberry as ruminant feeds in the dry season in central Vietnam. The Muntingia species is not suitable for repeated cutting.  

Nutritive value

The crude protein of the dry matter of the leaves and stems varied from 12 to 23 % (Table 2).  The NDF contents were high in all the plants.

 

Table 2: Chemical composition of Hibiscus rosa,  Muntingia,  Morus alba and Trichanthera ( dry matter basis except for DM which is on fresh basis)
	DM	CP	CF	Ash	NDF	ADF	Ca	P
Hibis. leaves	20.5	18.4	15.6	13.4	30.4	14.2
Hibis. leaves and young stems	20.0	17.2	17.9	13.4	34.0	19.0
Munt. leaves	37.0	16.0	14.1	11.6	24.5	12.6
Munt. leaves and young stems	40.0	14.3	20.2	12.0	34.7	22.6
Trichan. leaves	14.0	12.4	17.4	23.5	44.9	25.9
Trichan. leaves and young  stems	13.0	12.0	18.0	24.7	45.2	25.9
Morus 2. leaves	31.0	24.3	9.5	13.2	32.9	15.6	1.9	0.6
Morus 2. leaves and young stems	28.0	22.6	9.6	11.8	34.5	14.8	1.8	0.6
Morus 1. leaves	37.0	22.2	8.8	15.5	31.0	15.0	2.8	0.4
Morus 1. leaves and young stems	35.5	23.1	10.9	13.7	32.4	15.4	2.8	0.5

DM degradability at 24 h was highest for Hibiscus followed by Mulberry withlower values for Trichanthera and  Muntingia (Tabvle 3).

Table 3: In sacco degradability (mean values and SE) of leaves and stems of Morus alba, Hibiscus rosa, Muntingia and Trichanthera gigantea
	Incubation time (hr)
	8	16	24	48	72	96
Hibis. leaves	34.8±5.1	78.5±6.4	92.1±0.9	93.3±0.2	93.5±0.1	93.9±0.3
Hibis. leaves and young stems	44.3±1.6	55.1±1.3	71.9±1.8	89.5±1.2	91.2±0.4	91.4±0.3
Munt. leaves	30.6±0.5	33.9±2.7	39.6±6.2	67.1±3.3	75.2±0.5	79.1±1.9
Munt. leaves and young stems	32.5±0.6	36.5±1.8	46.5±4.2	63.8±1.7	68.7±1.0	70.1±0.7
Trichan. leaves	36.1±0.5	41.7±0.3	48.2±5.9	79.9±0.7	84.7±3.9	91.6±0.1
Trichan. leaves and young  stems	37.7±0.4	43.4±0.1	46.8±3.3	79.0±3.2	83.5±0.1	88.0±0.5
Morus 2. leaves	47.0±0.4	49.6±2.9	79.7±8.4	88.0±0.1	88.5±0.6	89.1±0.6
Morus 2. leaves and young stems	53.6±1.4	61.8±6.4	81.1±8.1	89.8±0.4	90.5±0.2	90.7±0.3
Morus 1. leaves	53.2±3.5	74.7±15.1	82.0±8.7	89.7±0.6	90.9±0.2	91.1±0.1
Morus 1. leaves and young stems	61.7±10.8	73.3±14.0	84.5±6.0	90.3±0.6	90.8±0.2	91.0±0.1

The washing loss (soluble cell contents) was higher for Mulberry than the other species.  The other  degradability parameters are difficult to interpret as apparently there are few differences among the species. However, it is known that the nutritive value of Trichanthera is relatively low when fed to goats (Keir et al 1997), whereas Mulberry has a high feeding value for goats (Kouch et al 2003).   

Table 4: In sacco degradability characteristics of Mulberry, Hibiscus, Muntingia and Trichanthera
	a (%)	b (%)	a + b (%)	c (%/hr)	Washing loss	ED of water insoluble (%)	Lag time (hr)
Hibis. leaves	-147	241	93.9	0.176	14.1	79.8	6.3
Hibis. leaves and young stems	17.4	76.2	93.6	0.050	15.5	78.1	0.0
Munt. leaves	16.0	77.5	93.5	0.019	28.2	65.3	9.0
Munt. leaves and young stems	18.3	56.5	74.8	0.030	30.1	44.7	7.9
Trichan. leaves	19.4	84.0	100	0.022	34.0	66.0	8.8
Trichan. leaves and young  stems	21.7	77.7	99.4	0.022	36.0	63.4	9.3
Morus 2. leaves	15.8	75.0	90.8	0.057	40.4	50.4	7.0
Morus 2. leaves and young stems	26.0	65.8	91.8	0.062	44.1	47.7	5.2

 

Gas production at 48ighest for Hibiscus followed by the Mulberry with lowest values for Trichanthera and Muntingia (Table 5). There were no consistencies, however, in the fitted curve parameters, which indicated higher rate constants for Mulberry compared with Hibiscus, yet 48h gas production showed the contrary.  The unreliability of the fitted curve procedures is shown in Figures 1 and 2. There was a close relationship (R² = 0.70) between the 48h degradation and gas production data (Figure 2) but no relationship (R² = 0.07) between the "a+b" parameters for the two methods (Figure 1).

 

Table 5: Gas production from the fermentation of  200 mg of DM of Mulberry, Hibiscus, Muntingia and Trichanthera
	Gas production, ml				Parameters
	24	48	72	96	a+b	c
Hibis. leaves	39.7	46.7	48.8	49.8	49.2	0.075
Hibis. leaves and young stems	35.2	41.4	43.4	45.0	44.0	0.075
Munt. leaves	15.7	23.8	27.4	29.4	31.7	0.027
Munt. leaves and young stems	11.6	19.5	20.0	21.7	22.8	0.033
Trichan. leaves	13.2	22.4	24.4	26.1	27.7	0.032
Trichan. leaves and young  stems	13.5	22.6	24.3	26.0	27.6	0.032
Morus 2. leaves	35.5	39.0	41.1	41.4	40.6	0.104
Morus 2. leaves and young stems	25.4	30.6	31.8	31.8	31.2	0.097
Morus 1. leaves	31.4	36.2	36.7	36.1	36.7	0.086
Morus 1. leaves and young stems	32.2	35.7	38.5	39.2	38.0	0.095

 

 

Figure 1: Relationship between a+b parameters for in sacco and gas production	Figure 2: Relationship between 48h in sacco DM degradation and gas production at 48h

 

Conclusions and recommendations

• Based on this study, it can be concluded that some indigenous trees together with the introduced Trichanthera gigantea can be grown as protein sources for ruminants in central Vietnam.

• These trees grow well in poor quality soil, at high ambient temperature, with low levels of management.

• Morus alba and Hibiscus rosa appear to have a higher nutritive value than Trichanthera gigantea with poorest values for the  Muntingia.

 

Acknowledgements

This research was partially financed by the bilateral SAREC project 2000-2002.

References

AOAC 1990 Official Methods of Analysis 13^th Edition. Association of Official Analytical Chemists, Washington DC

 

Keir Brenda, Dinh v. Binh, Preston T R and Orskov E R 1997b Nutritive value of leaves from  tropical trees and shrubs: 2. Intake, growth and digestibility studies with goats. Livestock Research for Rural Developement (9) 4:

 http://www.cipav.org.co/lrrd/lrrd9/4/bren942.htm

 

Leng R A 1997   Tree foliage in ruminant nutrition  APHP 139.  http://www.fao.org/docrep/003/w7448e/w7448e00.htm